General principle of Lignite Drying in a lignite fired plant is well known, using either hot flue gas extraction or steam extraction from Water & Steam cycle or both to supply the lignite drying system that includes beater mills, rotary drum dryers and/or fluidized bed dryer.
Lignite drying techniques have been developed and tested in order to use medium or low enthalpy heat to achieve partial or high level of lignite pre-drying before pulverization, and gain typically up to 3% point efficiency gains without heat recovery of evaporation vapour of lignite moisture or 5% point efficiency gains with heat recovery of evaporation vapour of lignite moisture. The heat is either originating from low pressure steam extraction, or from exhaust flue gas. These techniques sometime additionally use mechanical or chemical dewatering processes.
U.S. Pat. No. 8,661,821 B2 in which superheated steam, which has done partial work in a steam turbine, is extracted from a water/stem power cycle and used as a drying medium to evaporate moisture from coal powder. Condensate from the drying is then fed into a deaerator of the steam turbine via a condensate pump for recirculation. As discussed, the drying steam can be extracted from any number of steam extraction points contained in the water/steam power cycle.